Flanker Samu Manoa's 70th-minute try - he was driven over the line by his fellow forwards just seconds after Worcester's former Northampton flanker Neil Best received a yellow card - made the difference before referee Greg Garner awarded Saints a late penalty try.

It was only Saints' second win in their last five league games, but it took them into fifth spot, one point above Gloucester, who tackle Wasps tomorrow.

Hooker Hartley and lock Lawes were punished for killing the ball and a late challenge, respectively, yet Northampton had enough in the tank to prevail.

Northampton fly-half Stephen Myler kicked five penalties and a conversion for a 17-point haul, while his opposite Andy Goode landed six penalties out of seven, but it was not enough to stave off Warriors' fourth successive Premiership defeat.

Worcester have not won a league game since four days before Christmas, and they remain hovering above the relegation zone, although London Welsh, London Irish and Sale Sharks are all below them.

Worcester, beaten heavily by Bath last time out, were reinforced through Goode's recovery from illness and Scotland prop Euan Murray returning after RBS 6 Nations commitments that saw him start against England and Italy.

Hartley and Lawes, who made appearances off the bench during an impressive victory over Ireland in Dublin six days ago, both started for Saints, as did former red rose full-back Ben Foden.

Foden was immediately pressed into action, completing a superb try-saving tackle on Warriors wing Josh Drauniniu after Worcester cut Saints open with their first attack, but the game quickly settled into a goalkicking duel between Goode and Myler as both sides conceded penalties as though they were going out of fashion.

Goode, who is believed to be a possible target for Northampton next season, struck twice inside the opening eight minutes - his second penalty a 52-metre effort - before Myler completed a quickfire hat-trick.

Two further Goode penalties meant that Worcester held a 12-9 lead as half-time approached, but Myler then missed an opportunity to haul Saints level shortly after Hartley was sin-binned.

The game was punctuated by Garner's whistle, yet neither team could have had any genuine complaint with the official, who merely applied the letter of the law.

Myler booted his final penalty attempt of the half - the 10th across both teams - short, with Worcester narrowly deserving their interval advantage.

Myler kicked an equalising penalty within four minutes of the restart, although Worcester almost broke the try stalemate when impressive full-back Errie Claassens' 40-metre break needed three Saints defenders to halt it.

Worcester continued to look the more dangerous team with ball in hand, and they did not lack confidence to spin possession wide despite soft under-foot conditions. Northampton, in contrast, were happy to absorb whatever Warriors threw at them, keeping their defensive shape and securing sufficient quality field position for Myler to do the rest.

He duly obliged with his fifth successful penalty after 57 minutes that put Saints ahead for the first time, but Northampton were then back down to 14 men after Lawes' late challenge on Goode.

Goode dusted himself down to kick the resulting penalty, and the contest was level again entering a final quarter of an attritional encounter before another Myler shot bounced back off the post.

But Manoa's touchdown sealed the deal, despite Goode slotting another penalty, before a last-gasp penalty try that owed everything to a dominant Saints pack rubbed salt into Warriors' wounds.

Northampton finished the stronger team, and they now go forward to next weekend's home game against Bath with renewed confidence, while Worcester face local rivals Gloucester at Kingsholm on Friday night.

Northampton forwards coach Dorian West saluted his players for "grinding it out" after Saints put their play-off hopes back on track

It was only their second league win from their last five starts and was achieved despite Saints' England forwards Dylan Hartley and Courtney Lawes both being sin-binned.

"You need to be able to play the game depending on the conditions, and I was really pleased with how we did that today," West said. "It was not the conditions to be throwing the ball around, it was a day for grinding it out, working hard for each other and sticking tight in the forwards.

"I thought we played the conditions very well. We showed that in the second half when we controlled field position, got the ball in the right areas and our forwards worked really hard."

Worcester head coach Richard Hill refused to be despondent after the lost and was quick to praise his side's performance.

"We played some superb rugby," Hill said. "A year ago you wouldn't have seen Worcester play with that intent of producing 15-man rugby.

"We did not finish things off but we have just got to persevere with that type of rugby. It is the rugby the players want to play. Today we got beaten by a power game. We knew what was coming with the scrum and the lineout maul and we couldn't deal with it."